MS Excel Formula - Revised "IF Expression"

I understand that I need to utilize the IF in my expressions on MS Excel but I am receiving errors. So here is what I need help writing.
I need for cell B33 to perform the following operations based on what E21 reflects.

So if the value of E21 is 97% or less, then it needs to multiply B23 by 1.04;
if the value of E21 is 95% or less, then it needs to multiply B23 by .78;
if the value of E21 is 90% or less, then it needs to multiply E21 by .52;
if the value of E21 is 85% or less, then it needs to multiply E21 by .32;
if the value of E21 is 80% or less, then it needs to show 0.

How can I write this into cell B33 with no errors?