Step-by-step explanation:
Given that,
The frequency of oscillation, f = 0.5 Hz
(a) Let the length of the pendulum string is l. So,

T is time period, T = 1/f
So,

(b) When the elevator starts to accelerate upwards, new acceleration is a+g. If accelerating upward, the value of g has increased, because of inertia. So it will feel heavier and the period will decrease.