I have just worked out Lewis's probable tyre usage for the weekend.
FP1 2 sets of softs which will be handed back
FP2 1 set of softs + 1 set of supersofts Also handed back
FP3 1 set of softs + 1 set of supersofts Also handed back
Q1 1 set of softs
Q2 used set of softs and a new set of supersofts (to start the race on)
Q3 2 sets of supersofts one of which must be handed back
This leaves him with the two sets Pirelli mandate are for the race 1 Soft and 1 Medium with a used supersoft to start from Q2 (fastest time set on this), 1 new supersoft a used soft tyre set from Q1/Q2 and used supersoft set from Q3
This leaves him a race option of
SS-S-SS (new tyres at each pitstop) using the SS in the final stint when the car is at it's lightest and the track has rubbered in to get the maximum amount of laps possible.
Rosberg has 1 less set of softs so will probably run a set of mediums on the FP1 or FP2 as will Ferrari too.
Williams, Mclaren, RedBull, Torro Rosso and Haas have possibly expected to run the supersofts in Q1 so have asked for 7 sets each
Manor are doing their own thing and obviously trying to save money by only using 1 set of mediums all weekend

or maybe trying a one stop race to try and jump Haas and Sauber
Sauber and Force India are probably doing the same as Mercedes so are confident of getting out of Q1, or they were before the new qualifying format was sprung on them after they had made thier tyre choices!