tolong d jawab dengn caranya

harga sebuah pulpen
= Rp2.400,00

untung 20%
= 20 / 100 × Rp2.400,00
= Rp480,00

1 lusin = 12 buah
12 lusin = 12 × 12
12 lusin = 144 buah

harga pulpen 12 lusin ( 144 buah pulpen )
= 144 × Rp2.400,00
= Rp345.600,00 - ( Rp480,00 × 144 )
= Rp345.600,00 - Rp69.120,00
= Rp276.480,00 ( C )