I made the recurrence tree but I have no idea how I got the nlog(nfactorial) and why does the top part of the summation sign n-1 become n, this is what the solution shows but theres no clarification. please help. Thank you.

Ten) = T(n-1)+loon) login) Tn-1 log (n-1) Tin-27 login-2) Tin-i) Tog(n-i) niet logen-i) nzit logi) = log(n!) =nlog(n)