Using Johnson's rule for $2-$machine scheduling, the sequence is:

Six jobs are to be processed through a two$-$step operation. The first operation involves sanding, and the second involves painting. Processing

Six jobs are to be processed through a two$-$step operation. The first operation involves sanding, and the second involves painting. Processing

as follows:

For the schedule developed using Johnson's rule, the total length of time taken to complete the six jobs $($including the $2$nd operation$)=$ hours $($enter your response

as a whole number$).$