If the price of the keyboard only is increased, then the substitution effect of the price change will be negative.
What happens to the substitution effect ?
Perfect complements are goods that are used together in fixed proportions. For example, a keyboard and a computer are perfect complements because you need both of them to use a computer. When the price of one perfect complement increases, the demand for both goods decreases.
This is because the price increase makes the bundle of goodsmore expensive. As a result, consumers will be less likely to purchase the bundle of goods. Additionally, the price increase will make the computer a less attractive substitute for other goods, such as tablets or smartphones.