Consider all the esters of molecular formula $C_7{H}_{14}{O}_2$ , excluding stereoisomers. They are all treated with an excess of methyl magnesium iodide and then acidified to give alcohols. Each ester produces two different alcohols [excluding stereoisomers], both of which react with$B{r}_2/NaOH$ to give bromoform. The number of esters, satisfying all these criteria, is______.