Actually, Henry's Law is an empirical value. It means that it was not obtained out of raw calculations or correlations. This was gathered from experimental results. Hence, you can search its data. At standard temperature of 25°C (298 K),
k = k°e^[2400(1/T - 1/T°)], where k° = 29.4 L·atm/mol
Substituting the values so that T would be in 20°C or 293 K,
k = (29.4 L·atm/mol)e^[2400(1/293 - 1/298)]
k = 33.7 L·atm/mol
B. A new material is formed
Surface runoff, its quite obvious in the picture