Grapefruit-Lemongrass-Lime Infused Gin and a Gin & Tonic cocktail

Gin ((I used Bombay))

large Grapefruit (, peeled, pith removed, segmented and cut into 1-inch pieces)

5-inch stocks of Lemongrass (, each cut in half vertically if possible)

Lime (, peeled and cut into ¼-inch slices)

Grapefruit-Lemongrass-Lime infused Gin

Tonic to fill ((I used Fentimans))

Ice