42*25= 1050
2. Store B: 50*20= 1000
3. Point C 50*25= 1250 yuan
Every 100, returns 20, 1250. If 50 is removed, it is less than 100, and the remaining 1200 is greater than 100, and returns 100 * 20 = 240.
Actual cost1250-240 =1010 yuan.
So store b is the most affordable.