Every time a spinner is spun, the probability that it shows the number 4 is 0.2, independently of all other spins. (a) A pupil spins the spinner repeatedly until it shows the number 4. Find the mean of the number of spins required. [2] (b) Calculate the probability that the number of spins required is between 3 and 10 inclusive. [2] (c) Each pupil in a class of 30 spins the spinner until it shows the number 4. Out of the 30 pupils, the number of pupils who require at least 10 spins is denoted by X. Determine the variance of X. [4]