Which of the following statements are correct about this reaction?
1.  The given reaction follows SN2 mechanism.
2.  (b) and (d) have opposite configuration.
3.  (b) and (d) have same configuration.
4.  The given reaction follows SN1 mechanism

(a, b) In the given substitution reaction, the substrate is alky! halide which is primary type carbon having halogen atom. Here, a transitory state is existed in which one bond is broken and one hond is farmed simultaneously in single step. So, it will be according to SN2 mechanism. In this mechanism, nucleophile attacks the carbon just opposite to the leaving group, so the inversion of configuration will occur.