Determine the fertilizer N use efficiency of a cro of pigeon peas if the N application rate of fertilizer was175 kg/ha and its 15N abundance was 8.5%. The dry matter yield was 7 tonnes/ha, the 15N atom excess in the harvested crop was 2.0%, the total N content 1.25% and the N derived from fixation was 45%. Please show all stages to the answer.