Need help on the reasoning for the following ratios problem

[Optimist]

Need help on the workings for the following question, please.

It takes 5 minutes to fry a beef burger. One side of the beef burger takes 3 minutes to fry and the other side takes only 2 minutes. Two beef burgers can be placed on the frying pan at a time. What is the shortest time to fry all five beef burgers?

The answer is not 15 mins, it is 13 minutes.

Okanagan, a vaiety of answers are acceptable, however, one solution given is as below.

Let the 5 pancackes be a, b, c, d, e and the 2 sides of each pancake be 1 and 2 respectively.

Side 1 of a, Side 1 of b = 3 mins
Side 2 of a, Side 2 of b = 2 mins
(a and b are done)

Side 1 of c, side 1 of d = 3 mins
(remove c)

Side 2 of e, Side 2 of d = 2mins
(d is done)

Side 1 of e, Side 2 of c = 2mins
(c is done)

Side 1 of e = 1 min

Shortest time = 3+2+3+2+2+1 = 13 mins