Since the ECHO has a MTOW take-off weight of 2950 we must take a linear interpolation between the factors 1.15 for 2000kg and 1.25 for 3500kg. This results in a value of about 1.22. If you multiply a number by 1.22 it is the same as adding 22%.
(a) 1.15 for aeroplanes with maximum take-off weights of 2 000 kg or less;
(b) 1.25 for aeroplanes with maximum take-off weights of 3 500 kg or greater; or
(c) for aeroplanes with maximum take-off weights between 2 000 kg and 3 500 kg, a factor derived by linear interpolation between 1.15 and 1.25 according to the maximum take-off weight of the aeroplane.