There are 15 flowers in a plant of Pea. In each microsporangium of every stamen of all the flowers

There are 15 flowers in a plant of Pea. In each microsporangium of every stamen of all the flowers, there are 20 fertile microspore mother cells. How many pollen grain are formed from that plant?
(a) 12000
(b) 3200
(c) 48000
(d) 24000