Janet sends parcels by Parcel Express.
The table shows information about the cost of sending a parcel by Parcel Express.

Parcel Express
Weight range Cost
Less than 2 kg £3.80
2 kg to less than 5 kg £5.99
5 kg to 10 kg £7.14

The table below gives information about the numbers and weights of the parcels Janet sent in April and in May.

Number of parcels
Weight range April May
Less than 2 kg 23 21
2 kg to less than 5 kg 28 27
5 kg to 10 kg 19 32

Janet could have sent her parcels by Parcels R Go.
The table below shows information about the cost of sending a parcel by Parcels R Go.

Parcels R Go
Weight range Cost
0–15 kg £5.99

Janet thinks that it would have been cheaper to send all her parcels by Parcels R Go.

Is Janet right?
You must show your working.