Let the cost price be Rs 100 and amount of product be 100 gm
Now there is 50% markup so the marked price becomes Rs 150
Now after 10% discount on Marked price the selling price = Rs (150 - 15) = Rs 135
Now it is said that he only sale 80 % of the quantity So,
he is selling 80 gm in 135 Rs which means SP of 1 gm is = Rs 1.6875
Cost price of 1 gm = Rs 1
So profit percentage is 68.75 % ~ 68%