Probability of Household Grocery Spending

A survey was conducted among 100 households to determine their annual spending on groceries. The results showed that:

- 30 households spend between $200 and $300 per month.

- 40 households spend between $301 and $400 per month.

- 20 households spend between $401 and $500 per month.

- 10 households spend over $500 per month.

Based on this data, what is the probability that a randomly selected household spends less than $401 on groceries per month?