Hi all, I took my MGMAT today and got the following DS question. However the answer explanation seems to be contradicting. Please help.

Bob and Wendy left home to walk together to a restaurant for dinner. They started out walking at a constant pace of 3 mph. At precisely the halfway point, Bob realized he had forgotten to lock the front door of their home. Wendy continued on to the restaurant at the same constant pace. Meanwhile, Bob, traveling at a new constant speed on the same route, returned home to lock the door and then went to the restaurant to join Wendy. How long did Wendy have to wait for Bob at the restaurant?

(1) Bob’s average speed for the entire journey was 4 mph.

(2) On his journey, Bob spent 32 more minutes alone than he did walking with Wendy.

I chose (C) - both are required to answer this question. But OA per Manhattan is (B). Here is the explanaiton stated -

(2) SUFFICIENT: To see why this statement is sufficient, it is helpful to think of Bob's journey in two legs: the first leg walking together with Wendy (t1), and the second walking alone (t2). Bob's total travel time tb = t1 + t2. Because Wendy traveled halfway to the restaurant with Bob, her total travel time tw = 2t1. Substituting these expressions for tb – tw,

t1 + t2 – 2t1 = t2 – t1

tb – tw = t2 – t1

Statement (2) tells us that Bob spent 32 more minutes traveling alone than with Wendy. In other words, t2 – t1 = 32. Wendy waited at the restaurant for 32 minutes for Bob to arrive.

The correct answer is B.

My question is 32 minutes is not (t2-t1) but just "t2". Is that not true? Please let me know.

Thanks in advance