help?

Mandy begins bicycling west at 30 miles per hour at 11:00 A.M. If Liz leaves from the same point 20 minutes later bicycling west at 36 miles per hour, when will she catch Mandy?
a
1:30 P.M.

b
2:30 P.M.

c
2:00 P.M.

d
1:00 P.M.