An initial time study was done on a process with the following results $($in minutes$).$ Based on the data obtained so far, assuming an allowance of $20$ percent of the normal time, what do you estimate for the time per customer served, based on this preliminary sample?

$\backslash$table$[[$Element$,$Performance Rating,Observation $1,$Observation $2,$Observation $3,$Observation $4,$Observation $5],[$Element $1,70,4,3,5,4,3],[$Element $2,110,8,10,9,11,10],[$Element $3,90,6,8,7,7,6]]$