The duration of direct flights from London to Singapore in a particular year followed a normal

distribution with mean μ and standard deviation σ .

92 % of flights took under 13 hours, while only 12 % of flights took under 12 hours 35 minutes.

Find μ and σ to the nearest minute.

I'm stuck here, i put in the formula and then how do i find inverse normal? Step by step instructions? I have a TI84 if that helps.

Thanks