An all-equity firm worth $50 billion acquires for $4 billion cash a firm whose post acquisition value will be $6 billion. The acquiring firm had the cash and did not need to borrow. The current market value of the target is $3 billion. What is the estimated return to the shareholders of the acquiring firm?

a)2 percent.

b)4 percent.

c)6 percent.

d)8 percent.

The correct answer is (b) 4 percent.

Can you please show me how the calculation is done?