Your erection

Your mother points the calculator at you. "Boo!"

Fearing the worst, you instinctively put your hands up to shield your face. Your mother smiles and lowers the calculator slightly to point at your crotch.

She pushes a button. "Gotcha."

Zoe giggles, mesmerized by your still-stiff member, now once again bobbing in the open air.

Realizing you've been had, you move to cover yourself again, but your hands brushing against the head of your penis, combined with your sister's rapt attention, only serve to inflame it further.

Meanwhile, you mother is wandering through the kitchen, waving the calculator absently, murmuring "what to merge, what to merge...."

She stops. She smiles.