Excel query with regards to MAX/IF statements

I have what I hope is a simple, doable question, but that being said, I haven't been able to figure it out.

How can I alter the following code such that if F5 were 0, that the cell would display 0? In all other circumstances, it should display a minimum of '43'.

The latter part of the code works; i.e: the minimum that is displayed is 43, however, I don't know how to alter it so that if F5 were 0, it would display 0.

=MAX(SUM(IF(F5<=0,0,39),
IF(F5>30,(C5*0.08),
IF(F5>20,(C5*0.07),
IF(F5>10,(C5*0.06),
IF(F5>5,(C5*0.05),
IF(F5>2,(C5*0.04),
IF(F5>1,(C5*0.03),
IF(F5>=0.25,(C5*0.02),
IF(F5>=0,(0.03*C5*F5),0))))))))),43)

Thanks a lot!