Zytel Corporation produces cleaning compounds and solutions for industrial and household use. While most of its products are processed independently, a few are related. Grit 337, a coarse cleaning powder with many industrial uses, costs $1.60 a pound to make and sells for $2.00 a pound. A small portion of the annual production of this product is retained for further processing in the Mixing Department, where it is combined with several other ingredients to form a paste, which is marketed as a silver polish selling for $4.00 per jar. This further processing requires ¼ pound of Grit 337 per jar. Costs of other ingredients, labor, and variable overhead associated with this further processing amount to $2.50 per jar. Variable selling costs are $0.30 per jar. If the decision were made to cease production of the silver polish, $5,600 of Mixing Department fixed costs could be avoided. Zytel has limited production capacity for Grit 337, but unlimited demand for the cleaning powder. 

Required: 

Calculate the minimum number of jars of silver polish that would have to be sold to justify further processing of Grit 337.