Representing characters with ASCII and Unicode; representing images with pixels, colour depth, resolution and metadata; representing sound with sample rate, sample resolution and bit rate; and the effect on file size and quality.

Image size in bits is width times height times colour depth.

$200 \times 150 = 30000$ pixels. $30000 \times 3 = 90000$ bits.

Convert to bytes by dividing by 8: $90000 \div 8 = 11250$ bytes.

Markers reward the formula (pixels times colour depth), the correct bit total, and the conversion to bytes. Forgetting the divide-by-8, or multiplying by the colour depth wrongly, loses marks. Showing working secures method marks.

Sample rate is the number of samples taken per second (measured in hertz). A higher sample rate captures the sound wave more often, giving a more accurate, higher-quality recording, but it produces more samples per second so the file is larger.

Sample resolution (bit depth) is the number of bits used to store each sample. More bits per sample record the amplitude of each sample more precisely, improving quality, but again increase the file size because every sample takes more bits.

Markers reward linking each factor to both quality (more accurate capture) and file size (more data), and being clear that increasing either improves quality at the cost of a larger file.