A watermelon is assumed to be spherical in shape while it is growing. Its mass, \(M\) kg, and radius, \(r\) cm, are related by the formula \(M = kr^3\), where \(k\) is a constant. It is also assumed that the radius is increasing at a constant rate of 0.1 centimetres per day. On a particular day the radius is 10 cm and the mass is 3.2 kg. Find the value of \(k\) and the rate at which the mass is increasing on this day.