$5.$ I have waited $15$ minutes for my train to campus. I now hear a message saying the train is late and will arrive $7$ minutes from now.

I am deciding whether to continue waiting, or get in a rideshare that will pick me up right away. The travel time on train and rideshare is the same.

My opportunity cost of waiting is $\_\_\_\_\_$ of my time.

A$)7$ minutes

B$)8$ minutes

C$)15$ minutes

D$)22$ minutes

$-$ E