- $ a \\\in \\\left( {10;\\\left. {12} \\\right]} \\\right.$.
- $ a \\\in \\\left( {16;\\\left. {18} \\\right]} \\\right.$.
- $ a \\\in \\\left( {12;\\\left. {14} \\\right]} \\\right.$.
- $ a \\\in \\\left( {14;\\\left. {16} \\\right]} \\\right.$.