Solution -
CP of washing machine = 10000
10% discount,
CP after 10% discount = 10000 (90/100)
= 9000
Again,
20% discount,
CP after 20% discount = 9000 (80/100)
= 7200
He spends 10% of his CP on tansport.
CP = 7200 (110/100)
CP = 7920
SP = 7920 (110/100)
SP = 8712
Therefore,
He should sell the washing machine at Rs. 8712 to earn a profit of 10%.
Hence,
The correct answer is option (c) 8712.
Thank You