Please show me step by step to solve the math question. Thanks you.

Please show me step by step to solve the math question. And please provide the correct answer. Thanks you.

The length of human pregnancies (with no complications) from conception to birth varies according to a normal distribution with mean 260 days and standard deviation 10.

Only ten-percent of pregnancy lengths are less than what value?

Question 32 options:

259 days

261 days

250 days

247 days

273 days