Answer:
Using the De Morgan Rule
!(A && B) is equivalent to !A && !B
the expression
        boolean oilOK =  !( months >= 3 || miles >= 3000 ); 
is equivalent to
        boolean oilOK =  !( months >= 3 ) && !( miles >= 3000 ); 
which can be further transformed to
       boolean oilOK =  ( months <  3 ) &&  ( miles <  3000 );

Free Shipping

For an on-line shopping site, shipping is free for purchases of $50 or more, unless the merchandise is on sale.

boolean freeShipping =  purchase >= 50 && !onSale; 

Here is an expression that shows when to charge for shipping:

boolean shipping =  !( purchase >= 50 && !onSale ); 

Assume that onSale is a boolean variable.

Question 16:
Rewrite the second expression in two steps. In the first step, apply De Morgan's rule that !(A && B) is equivalent to !(A) || !(B).
boolean shipping =   
In the second step, rewrite the relational expression:  
boolean shipping =