Arse end of straight NL100

[chrispy1]

Utg is 18/15/6 over 400 hands

Button ($124.50)
SB ($120.15)
BB ($77.75)
UTG UTG ($108)
UTG+1 Hero ($110.70)
CO ($206.20)

Preflop: Hero is UTG+1 with 4s 4c
UTG raises to 4, Hero calls 4, 4 folds.

Flop (9.50) 6s 8c 7h
UTG bets 7, Hero calls 7.

Turn (23.50) 5s
UTG bets 18, Hero calls 18.

River (59.50) 2d
UTG bets 79, ...Hero?

whats villains range?