Use the Following General Linear Supply Function to Answer the Next

Use the following general linear supply function to answer the next 6 questions:

where is the quantity supplied of the good, P_I is the price of the good, is the price of an input, and F is the number of firms producing the good.
-Again suppose = $40 and F = 50, what is the lowest price that will induce firms to supply 400 units of output?

A) $15
B) $20
C) $25
D) $30
E) $35