Ah Mass and Boulois, one of my favourites....
Q1. First see if you can use the running load limitation of 350 kg/m to remove some answers. To do this take the mass of the box (500kg) and divide it by the longest edge of each box. Doing this you will find that the 142cm box has a running load of 352kg/m, which is out of limits, so you can rule out number 2, all the others are in the running load limit.
Next you want to see what the distribution loading limits are like, to do this work out the biggest area that each box could be then divide the mass of the box by the areas to see which ones are in limits, so for the answers:
1) 1.1m x 1.45m = 1.595 m2, 500/1.595 = 313.48 kg/m2
2) out of running load limit
3) 1.4m x 1.43m = 2.002 m2, 500/2.002 = 249.75 kg/m2
4) 1.35m x 1.44m = 1.944m2, 500/1.944 = 257.2 kg/m2
So boxes 3 and 4 are both able to be carried!
Q2. First you need to work out the actual take off mass, you get this by taking the expected landing mass at original destination (4600kg) and adding the trip fuel to original destination (6000kg), so the actual TOM is 10600kg. You know the actual flight time is 2 hrs and fuel burn is 1500kg per hour so 10600-(2x1500) = 7600 kg for landing mass; PLLM is 9000kg, so you are okay to land - the rest of the info is there to confuse you!
Q3. This is easiest to do by using a pencil on the sample load sheet at the back of CAP 697/8 (whichever one it is), just write the figures in the relevant box and you take the most limiting one. A trap on this question is that STOM is less than PLTOM!!! I don't have my CAP manual anymore and my hangover is preventing me from working this through in my brain, but if you use the CAP manual it should make sense.
BigAir