A showroom contains shirts of three sizes i.e. 'M', 'L' and 'XL', in the ratio 4:6:9, respectively. If the total number of shirts in the showroom in 3 80 and the ratio of number of black and blue XL size shirts are 2: 1, respectively, then what is the number of black XL size shirts in the showroom given that 'XL' size shirts are either blaack or blue?
