Calculate Anita's total monthly phone bill based on her call and SMS usage. The plan includes a N100 monthly contract cost. Peak time SMS cost N0.85 each, and off-peak SMS cost N0.25 each. Anita sent

The cost per peak time SMS is 85 cents, which is N0.85.
Anita sent 45 SMS during peak time.

$$\text{Peak time SMS cost} = 45 \times \text{N}0.85 = \text{N}38.25$$

The cost per off-peak time SMS is 25 cents, which is N0.25.
Anita sent 105 SMS during off-peak time.

$$\text{Off-peak time SMS cost} = 105 \times \text{N}0.25 = \text{N}26.25$$

The total monthly bill is the sum of the monthly contract cost, peak time SMS cost, and off-peak time SMS cost.

$$\text{Total monthly bill} = \text{N}100 + \text{N}38.25 + \text{N}26.25$$ $$\text{Total monthly bill} = \text{N}164.50$$

The total monthly bill will be $\text{N}164.50$.