Fixed rate shipping features

hi I have set up a fixed rate of ￡4 + ￡1 for each additional products.

the client wants to have two price points eg:

tshirts ￡4

mugs ￡3

the if someone adds 2 T-shirts and a mug it would charge the highest postage (￡4) and add ￡2 for the two additional items.

can I do this with fixed rate?

thank

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