Unless there is a big ramp up in Wk2, it will be very hard to clear the shop.

40 Stamina map gives 20 Bars. 480 Stamina a day = 240 Bars.

20 Chocolate Bars is 50 Sweet-hearts (50,000 hp Boss), so that is 600 hearts a day at the x1 rate, or 7,800 for the 13 days.

At the x10 rate, you can convert your 240 Bars to 3x75, or 1,500 Sweet-hearts a day (with 5 bars left over). Over 13 days, that is 19,500 Sweet-hearts plus 65 Bars left over, which is another 150 Sweet-hearts.

For higher level squads it seems it isn't worth fighting the weak 1 boss as it is so weak (50,000 hp for the 20 bars)?
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Edit - just read more - the Boss HP goes up after each one is defeated. Also, I am not sure the x10 bonus works on the bosses that don't have enough HP to take the extra damage.