The operation is defined for all integers a and b by the equation ab = (a - 1)(b - 1). If y10 = 90, what is the value of y ?  Choose the correct choice from the following options:	A) 10	B) 12	C) 15	D) 11	E) 20
ab = (a - 1)(b - 1)   y10 = (y-1)(10-1) = 90 --&gt; y-1=10 --&gt; y=11   Answer: 11
<result>D</result>
The operation is defined for all integers a and b by the equation ab = (a - 1)(b - 1). If y10 = 90, what is the value of y ?