Answer this question with respect to the PERT problem posted in Canvas $.\backslash$table$[[1,$Month,Demand D$($t$)],[2,1,70],[3,2,65],[4,3,92],[5,4,84],[6,5,91],[7,6,93],[8,7,99],[9,8,97],[10,9,99],[11,10,100],[12,11,103]]$ What is the variance of task C$?$