The values of cubic forms at prime arguments

Let λ1, λ2, λ3, λ4, λ5 be non-zero real numbers, not all negative. Let V be a well-spaced sequence, δ>0. If λ1/λ2 is irrational and algebraic, then we prove that E(V,X,δ)≪X17/18+2δ+ε, where E(V,X,δ) denotes the number of v∈V with v≤X such that the inequality |λ1p13+λ2p23+λ3p33+λ4p43+λ5p53−v|