Correct option is C
Market price = Rs. 300
Discount = 50% of Rs. 300 = (50/100) x 300 = Rs. 150
Selling price = Market price - Discount = 300 - 150 = Rs. 150
Let the cost price be 'C'.
Profit = 50% of C = (50/100) x C = 0.5C
Selling price = Cost price + Profit
150 = C + 0.5C
150 = 1.5C
C = 150 / 1.5 = 100
Therefore, the cost price is Rs. 100.