∴ Total amount spent by all three together = 1 × 1000 + 200 × m + 15 × 50 = 1750 + 200m.
Now since one of them buys a large bag (worth Rs. 1000) that person spends at least Rs. 1000.
∴ Each of them spends at least Rs. 1000 and hence total amount spent by them together is at least Rs. 3000.
∴ Minimum value of m can be 7.
If 7 medium bags are sold. Total amount spent = 1750 + 200 × 7 = 3150
∴ Minimum number of medium size bags sold = 7.
Hence, option (a).