Calculate probability in graphical model

I have the following graphical model, in which I wish to compute $ p(Intelligence = 1|Letter = 1, SAT = 1)$

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I tried using Bayes, and also just without Bayes as $ p(D,I,G,L,S)=p(D)p(I)p(G|D,I)p(S|I)p(L|G)$ but im stuck, here, when I for example trie to calculate $ p(G|D,I)$ .