The period of a pendulum is the time the pendulum takes to swing back and forth one full time. the function i = 0.81t^2 relates the length l in feet of a pendulum to the time t in seconds that it takes to swing back and forth. the convention center in portland, oregon, has the longest pendulum in the u. s. the pendulum’s length is 90 ft. find the period for this pendulum.

a. 8.5 seconds
b. 10.5 seconds
c. 90 seconds
d. 111 seconds