Since tea and coffee sales are independent the joint distribution of their sold amounts in a minute is the product of their individual distributions.

Coffee sales are Poisson w/mean $\lambda_c=1.5$

Tea sales are Poisson w/mean $\lambda_t=0.5$

So the Joint PMF is given by

$p_{C,T}(c,t)=\left(\dfrac{(1.5)^c}{c!}e^{-1.5}\right)\left(\dfrac{(0.5)^t}{t!}e^{-0.5}\right)$

for (i) simply plug (1,1) in for (c,t)

for (ii) just recast things to be over the course of 3 minutes rather than 1.

Coffee sales are now Poisson with $\lambda_c=3*1.5=4.5$

Similarly Tea sales are now Poisson with $\lambda_t=1.5$

You should be able to finish from here.