When the price of capital rises, the firm will want to produce less output now that an input price has risen. When the price of capital rises, for a given level of output, the firm will want to substitute workers for the relatively expensive capital. Therefore, there may be job creation or job destruction as a result of removing the investment tax credits. It depends upon the relative sizes of the output and the substitution effects. The market for tomatoes is perfectly competitive with constant costs.
Demand shifts up due to the price of lettuce decreasing.
This shifts the supply curve up, to the point where all firms make zero profits again.