What is the lower quartile of the data set 25,8,10,35,5,45,40,30,20?

To calculate lower quartile firstly arrange the data set from minimum to maximum.
So, series is : 5,8,10,20,25,30,35,40,45
then, find out the minimum and center number from that data set.
Minimum number = 5 and center number = 25
then, add together minimum and center number and divided by 2,
so, (25+5)/2 = 30/2 = 15
so, lower quartile = 15