(a) By how much is the sum of \(3\frac{2}{3}\) and \(2\frac{1}{5}\) less than 7?

(b) The height, h m, of a dock above sea level is given by \(h = 6 + 4\cos (15p)°, 0 < p < 6\). Find :

(i) the value of h when p = 4 ; (ii) correct to two significant figures, the value of p when h = 9 m.