What is the cost basis for my RSU? My 1099-B says $0

Block 14 of my W2 says $40,000 RSU. My paystub itemized the $15,000 tax deductions (fed, state, SSA, etc..). Out of the remaining $25,000, twenty thousand dollars were deposited to my E-Trade account, kept it there and did not sell. The remaining $5,000, although I did not receive, was added to my total income and taxes deducted from it. Will my cost basis be $25,000 so that the $5,000 will be deducted from my total income.

Further explanation:
My employer sold 400 shares of company stock @ $100 per share ($40,000 total) and paid to me as my year’s RSU indicated at block 14 of my W2 form. Fifteen thousand dollar taxes were deducted from the $40K as indicated by my paystub. Out of the remaining $25,000, two hundred shares of company stock at $100 per share ($20,000 total) were deposited to my E-Trade account (I kept it invested and did not sell). The rest, $5,000, which is part of my year’s income and paid taxes to it was unaccounted for. My 1099-B from E-trade says the cost basis is 0. You were right that if I put cost basis as 0, I will be double taxed. However, if I put my cost basis as $20,000, what happened to the unaccounted $5,000. To me it make sense to put $25,000 as my cost basis because that’s how much it cost to get my vested $20,000 RSU. It also resolved the question about the $5,000 shortfall.
I asked my payroll as some of you suggested but I was told to ask E-trade or hire a tax professional. E-trade does not know what the cost basis was that’s why they put 0. I have been doing my taxes since I started working and it pains me to think that I can’t solve what seems to me a minor problem that I might need a tax professional to do what I have been doing for quite a while (That’s my pride talking) I might need their help this time around. However, besides my math was wrong, talk to my employer or ask e-trade, is there any other answer there? Appreciate your help.

Found it!
To all those good people who tried to help, I found the answer. I followed the advice of my peers and searched all the documents I can get from my E-Trade account. I found the "Stock Plan Transaction Supplement" that has a column that says "adjusted cost basis" of $19,900. The form still says $0 on its "cost basis’ column just like the 1099-B but with a "adjusted cost basis" column that the 1099-B lacks. I cancelled my appointment to a tax accountant and filed my return myself. I felt marvelous. Thank you all for your efforts.

BTW, I rounded up all the numbers so as not to confuse. The missing $5,000? It wasn’t, It is on my W-2 and paystub, which means it was paid to me.