$(i)$ Give one example with a chemical equation for the following reactions:
$(a)$ Substitution reaction.
$(b)$ Saponification reaction.
$(c)$ Combustion reaction.

(N/A) Substitution reaction: Methane reacts with chlorine in the presence of sunlight to form chloromethane and hydrogen chloride.
$CH_4 + Cl_2 \xrightarrow{\text{Sunlight}} CH_3Cl + HCl$
$(b)$ Saponification reaction: Ethyl acetate reacts with sodium hydroxide to form ethanol and sodium acetate.
$CH_3COOC_2H_5 + NaOH \longrightarrow C_2H_5OH + CH_3COONa$
$(c)$ Combustion reaction: Methane burns in oxygen to produce carbon dioxide,water,and heat energy.
$CH_4 + 2O_2 \longrightarrow CO_2 + 2H_2O + \text{Heat} + \text{Light}$