Hi, I need help with an economics problem (game theory). Just 1 problem if someone can help.

a)
If bidder i choose her bid less than other he would lose the auction and her expected pay off will be zero.
When bidder i choose her bid bi greater than other he would win and her expected pay off will be vi – bi.
Linear strategy bi (vi) = a + cvi
    vi = (bi –a) /c
Expected pay off of bidder i when he chose...