For amounts over 35,000 units, in house option A is cheaper.
Find the break even quantity (aka make the equations equal) of the outside vendor compared to each in-house option.
Vendor vs in house option A:
10x = 175,000 + 5x (subtract 5x from both sides)
5x = 175,000 (divide by 5)
x = 35,000 units
vendor is cheaper than option A up to 35,000 units
Vendor vs. in-house option B
10x = 190,000 + 4x (subtract 4x from both sides)
6x = 190,000 (divide by 6)
x = 31,667 (rounded to nearest unit)
vendor is cheaper than option B up to 31,667 units