Opps...how should i answer

Everytime after Kelvin poo poo, we will wash his bum bum with water. While we were in my parents house, Kelvin looked for daddy ..........

Kelvin: where is daddy?
Ah Ma : daddy is in toilet, he poo poo
Kelvin: daddy poo poo, who wash daddy’s bum bum?
Ah Ma : **oopps, doesn't know how to answer** daddy will wash him bum bum himself

Whem mom told me her conversation with Kelvin, both of us had good laugh over it.