(I need the answer ASAP in 10mins)

Joe is deciding whether he should buy painting supplies online or at the store. To buy the supplies at the store, he needs to travel to the art supply store 15 minutes away from his home. Although he does not need to spend any time at the store, he loses time traveling to and back from the store. The price of painting supplies is $18 if he buys at the store.

If he buys the painting supplies online, he does not lose any time. However, the painting supplies cost $30.

Suppose that if he doesn't travel to the store, he can use that time to work and earn $30 per hour. Answer the next three questions based on this information.

What is the opportunity cost of traveling to the store for Joe?

What is the total cost of buying the painting supplies at the store?