Let Ram's rate of working be R (fraction of the job completed per day). Let Shyam's rate of working be S (fraction of the job completed per day).

Together, Ram and Shyam work for 4 days to complete 60% of the job: $4(R + S) = 0.60$ So, $R + S = 0.60 / 4 = 0.15$ (Equation 1)

After Ram leaves, Shyam works for 8 more days to complete the job: $8S = 0.40$ (since 60% is already completed, and 40% remains)

So, $S = 0.40 / 8 = 0.05$ (Equation 2)

Now substitute the value of S in Equation 1: $R + 0.05 = 0.15$ $R = 0.15 - 0.05 = 0.10$

The time taken by Ram to complete the entire job alone is: Time = $1 / R = 1 / 0.10 = 10$ days