A Level Normal Distribution question

Hi, I've been looking at this question for nearly an hournow and I can't figure out what to do, I've looked through my notes and my textbook and nothing helps so could someone please talk me through what I need to do?

**Question:**

1. An athlete believes that her times for running 200 metres in races are normally distributed

with a mean of 22.8 seconds.

(a) Given that her time is over 23.3 seconds in 20% of her races, calculate the variance of

her times.

[5 marks]

(b) The record over this distance for women at her club is 21.82 seconds. According to her

model, what is the chance that she will beat this record in her next race?

[3 marks]

Thanks so much in advance