solve this please

Q1- Two plants were installed by a certain textile mills on the same date and weft in operations under similar conditions. Their first six month's output is given below; MONTHS Plant I Plant II [units) (units) January 10,000 20,000 February 30.000 25,000 March 10,000 25,000 April 25.000 May 45,000 30,000 June 25,000 10.000 Total 150-000 135,000 Required: Calculate the variance in output for these two plants