Bethany knits hats and scarves. A hat takes her 1.5 days, and a scarf takes her 4 days. Bethany recently spent 18 days knitting 7 items. Write and solve the system of equations to find the number of hats (h) and the number of scarves (s) that Bethany knitted.

3hats, 4 scarves

2hats, 5 scarves

4 hats, 3 scarves

5 hats, 2 scarves