SallyMay's cable company promised 40 megabits per second (Mbps) of internet download speed when she purchased the service. Once the service was provided, she tested her download speed for a 24-hour period. The following graph shows the test result. Define this function B(t) to model the download speed, in Mbps, where t is the number of hours since 0:00 a.m. on the day the test was conducted.

45 Download Speed in Mbps 40 35 30 25 20 15 10 5 0 2 4 Hours Since 0:00AM 6 8 10 12 14 16 18 20 22 24